Portions of CORG documentation should be release-dependent

https://doc.nuxeo.com/corg/unit-testing/#jetty-feature , for instance, is not valid anymore since Nuxeo 10.2 and NXP-24493.

The CORG documentation should be updated when changes happen but still be valid for older releases...
There might thus be a need to have the Developer Guide documentation updated with a way to decipher the releases for which a particular way of doing is valid and when a change is introduced.